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b=R12gHDtdlxbeRxELb6SDgKRtfj+fwZDLOVEpZbQePGw/nOQkWaIQmCuDI88nfJzjA IvoPuBSlLHbh51k40ngxIIwP5OZdeneUpOoMHc67EXoAwGqsqgO91UO5zMToC3iRCx os6a4JKHG09hrtwLjQ0sBr103Tb+FDBljP9trJsDylI8qBKsBcFpgEM06fPZIBnK+m Z1PfibgbcUoBPJ2c2tVtio6byjaWZeRjA7L/5NWRom4Xuq/UjoamHHyhW6pc4NTJ7c eoatT3argSs6R56MGCPFYQf8u6vroYxOzLuldNUHRCxSN9gkAHhdYYEA/zQ6JKI13W vC3sEOjH4p1Kw== Message-ID: <878faef6-bbd3-43ec-af82-6da675a5f8fe@kernel.org> Date: Tue, 9 Jun 2026 12:21:34 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 6/9] dax: plumb hotplug online_type through dax To: Gregory Price , sashiko-reviews@lists.linux.dev Cc: linux-mm@kvack.org References: <20260605211911.2160954-7-gourry@gourry.net> <20260605213143.A18F01F00893@smtp.kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 836B42000B X-Stat-Signature: 179mtpqkr7ejxa3r36temxgi3ytkqy8e X-HE-Tag: 1781000497-370840 X-HE-Meta: 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 QiFqN7mv GXLwtzFf/K6uOsf/Oqff6A9eZ/OsnvVrPliIUxBoFz23Mw7P8uU0P9qIXNwYL9uILHyFU79YHE+R7Kbuu/78XScCrODvSXH7cOdWz7seDxW+xoBq7gQCTDBVjnSFj+0THu6KtJMocTadYQNNXF2LJ5JaUimCfg6vFSVn6fsp9Cgy6HPDDYILNKYTbijFC2Bv0IO+gi/nJYcgDBVMi7+08aB8oxsyL7GNlZ59Yhx7VtAm3Ye1Apcj4mYoJRGCTxhfWDKXKkoFUi3LtKMzhHZHun9U7M8W1SSPaGKaX+8ubuDQMjEukECwCJuNTkxSBRQPNKrzUVrtz2n5bFv9nFFkoveOLNlDWmXhPLyRvDzdw0WzO7q2Nrr+wmW/ztDD4YT2wA6VF Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/5/26 23:54, Gregory Price wrote: > On Fri, Jun 05, 2026 at 09:31:43PM +0000, sashiko-bot@kernel.org wrote: >> >>> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c >>> index 592171ec10f49..41ccb618a1464 100644 >>> --- a/drivers/dax/kmem.c >>> +++ b/drivers/dax/kmem.c >>> @@ -172,8 +172,9 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) >>> * Ensure that future kexec'd kernels will not treat >>> * this as RAM automatically. >>> */ >>> - rc = add_memory_driver_managed(data->mgid, range.start, >>> - range_len(&range), kmem_name, mhp_flags); >>> + rc = __add_memory_driver_managed(data->mgid, range.start, >>> + range_len(&range), kmem_name, mhp_flags, >>> + dev_dax->online_type); >> >> [Severity: High] >> Does capturing the auto-online policy at device creation time break dynamic >> sysfs policy changes? >> > > @David - we talked about this ~6+ mo ago at this point, i originally > proposed something like MMOP_SYSTEM_DEFAULT > > https://lore.kernel.org/linux-mm/20260114085201.3222597-3-gourry@gourry.net/ > > https://lore.kernel.org/linux-mm/c4ed9675-269c-4764-86d5-87f4f83fc74d@kernel.org/ > > ''' > I don't like having fake options as part of this interface. > > Why can't we let selected users use mhp_get_default_online_type() > instead? Like add_memory_resource(). We can export that function. > ''' > > I guess the argument here is that the value can't be cached? > > But we can't really enforce that. > > This is a behavioral change we have to agree on (either we change it or > carry something like MMOP_SYSTEM_DEFAULT for this). I don't think we'd need a generic MMOP_* for that purpose (the core cannot really do a lot with that AFAIKS, and the scenario "unspecified" doesn't really occur in memory hotplug core). I guess you could have some indication whether the user already configured it manually (bool online_type_specified), and handle that in the handful of places. if (dev_dax->online_type_specified) online_type = dev_dax->online_type; else online_type = mhp_get_default_online_type(); Of course, you could also just call the old interface when adding without a preference. A negative online_type could also be used as "unspecified" in your code (MMOP_ starts at 0). But the question really is which semantics we would want? is that exposed to user-space somehow, such that the user could query it ("default")? or how does this get set, and how does it later get used while it could have changed system-wide? -- Cheers, David